linux-kernel - Re: [PATCH 3/3] ovl: redirect on rename-dir

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Date:   Wed, 26 Oct 2016 14:51:40 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Amir Goldstein <amir73il@...il.com>
Cc:     Miklos Szeredi <mszeredi@...hat.com>,
        "linux-unionfs@...r.kernel.org" <linux-unionfs@...r.kernel.org>,
        Guillem Jover <guillem@...ian.org>,
        Raphael Hertzog <hertzog@...ian.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] ovl: redirect on rename-dir

On Wed, Oct 26, 2016 at 2:11 PM, Amir Goldstein <amir73il@...il.com> wrote:
> On Wed, Oct 26, 2016 at 2:26 PM, Miklos Szeredi <miklos@...redi.hu> wrote:
>> On Tue, Oct 25, 2016 at 2:49 PM, Amir Goldstein <amir73il@...il.com> wrote:
>>
>>>> @@ -880,31 +913,34 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
>>>>         if (WARN_ON(olddentry->d_inode == newdentry->d_inode))
>>>>                 goto out_dput;
>>>>
>>>> -       if (is_dir && !old_opaque && ovl_lower_positive(new)) {
>>>> -               err = ovl_set_opaque(olddentry);
>>>> -               if (err)
>>>> -                       goto out_dput;
>>>> -               ovl_dentry_set_opaque(old, true);
>>>> +       if (is_dir) {
>>>> +               if (ovl_type_merge_or_lower(old)) {
>>>> +                       err = ovl_set_redirect(old);
>>>
>>> There is a fair chance of getting ENOSPC/EDQUOT here and confuse user space.
>>> Would it be better to convert these non fatal errors with EXDEV, so
>>> user space will
>>> gracefully fallback to recursive rename/clone/copy?
>>
>> Recursive copy up will surely consume more space than an xattr?
>
> Surely. But that is not what I meant.
> In Ext4, for example, the total size of extended attributes for an
> inode is limited to a single block,
> so you can get ENOSPC with alot of free space in the file system.

Ah.

>
> You can also get ERANGE if the redirect path length > 256.

The 256 limit is for the name of the xattr, not the value.

Thanks,
Miklos